Extract from giant knotweed (Reynoutria sachalinensis) sold as MILSANA® and REGALIA® by Marrone Bio Innovations, Inc. provides control of powdery mildew and other plant diseases on cucurbits and other crops mainly by inducing an accumulation of fungitoxic phenolic compounds in the plant (Daayf et al., 1995; Wurms et al. 1999; Schmitt, 2002). Recently, formulated giant knotweed extract has also shown great efficiency in inducing resistance in various crops against plant pathogens including wheat powdery mildew (Vechet et al., 2009). Besides the induced systemic resistance (ISR) mode of action, the formulated R. sachalinensis extract has recently also been shown to have a direct fungistatic effect against wheat powdery mildew (Blumeria graminis f. sp. tritici; Randoux et al., 2008).
Plant defense inducers such as the extract of Reynoutria sachalinensis have been tested in tank mixes and rotations with other SAR/ISR products as well as with biocontrol agents (BCA) (Hafez et al., 1999; Belanger and Benyagoub, 1997; Schmitt et al. 2002; Schmitt and Seddon, 2005; Bardin et al., 2008). The purpose of these studies has mainly been to demonstrate the compatibility of different types of plant extracts with biocontrol agents. Konstatinidou-Doltsinis et al. (2007) tested the R. sachalinensis product in a rotation with Pseudozyma flocculosa product against powdery mildew on grapes, and found that alternated application of both products improved the efficacy of R. sachalinensis. In the same study, alternation of sulfur and R. sachalinensis in a rotation did not have a beneficial effect. Belanger and Benyagoub (1997) found that the yeast-like fungus, Pseudozyma flocculosa, was compatible with Reynoutria sachalinensis when used against cucumber powdery mildew in a greenhouse. Similarly, Bokshi et al. (2008) evaluated the combined effect of an acquired systemic resistance activator benzothiadiazole and MILSANA® against cucumber powdery mildew, and found that MILSANA® used in a rotation with benzothiadiazole provided an effective control measure against powdery mildew in the field. However, based on the disease severity and yield data collected, it was not possible to determine whether the positive effect was additive or synergistic.